Localized congestion exposure

ABSTRACT

A method of localized congestion exposure within a local loop in a cellular network that is performed by a localized congestion exposure sender node of the local loop. The method includes receiving downlink packets that are destined for a downstream user device. The method also includes receiving packets that have feedback indicating a congestion level from a downstream node of the cellular network. The method further includes inserting a declaration of an expected downstream congestion level into headers of the received downlink packets; and forwarding the downlink packets that have the declaration of the expected downstream congestion level inserted into the headers toward the downstream user device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 12/976,067,filed Dec. 22, 2010, which claims the benefit of U.S. ProvisionalApplication No. 61/378,980, filed Sep. 1, 2010, which are herebyincorporated by reference.

FIELD

Embodiments of the invention relate to the field of networking; and morespecifically, to congestion avoidance in the field of networking.

BACKGROUND

Network congestion may occur when more packets or data are transmittedthrough a network than the network can accommodate. The networktypically has a fixed capacity, such as a fixed bandwidth or a fixedpacket transmission rate. When more packets need to be transferred thanthe fixed capacity of the network, the network may employ queues tobuffer the packets to accommodate such traffic surges. However, thenetwork elements generally have queues and other resources of a fixsize. The network congestion may occur when these fixed sized resourcesare nearly or fully utilized (e.g., the queues may be nearly full) andare not able to accommodate additional packet transmissions.Conventionally, networks experiencing such congestion may simply droppackets. However, dropping packets may have certain drawbacks, such ascausing retransmission of the dropped packets, which may furthercontribute to or prolong the network congestion.

Explicit Congestion Notification (ECN) is a known congestion avoidancescheme that involves marking packets instead of dropping them in thecase of incipient congestion. An ECN-aware network element experiencingincipient congestion may mark ECN fields in headers of the packets toindicate that the congestion is occurring, instead of dropping thepackets. By way of example, ECN may use two least significant bits inthe DiffSery field in the IP protocol header (IPv4 or IPv6) which areassigned to the ECN field to encode four different ECN code-points. AnECN code-point of 00 may indicate not ECN-capable transport (i.e., notECT) if either end-point does not support, or is not willing to support,ECN-capable transport. Either of two ECN code-points, namely 10 or 01(ECT(0) and ECT(1) respectively), may indicate ECN-capable transport(ECT). An ECN code-point of 11 may indicate that congestion has beenexperienced or encountered (ECN-CE). For example, an ECN-capable node orqueue may probabilistically set the ECN field to 11 if congestion isencountered or experienced and then forward the ECN-marked packet. Toavoid heavy congestion, routers and other network elements may markpackets with probability depending on an average queue length. Examplesof suitable protocols to specify the feedback for ECN include TCP, DCCP,SCTP, and RTP/UDP. The percentage or proportion of packets marked may beindicative of, and directly related to, the level of congestion in thenetwork. In ECN, an end-point receiver of the ECN-marked packets mayreturn feedback or information about the percentage or proportion ofmarked packets, or the level of congestion, to the sender in order toinform the sender that the network is experiencing congestion. Thesender is expected to decrease its transmit rate so that future packetsare not dropped. Advantageously, ECN may help to reduce the amount ofcongestion in the network and the number of packets that are dropped.

Congestion exposure (ConEx) is another congestion avoidance scheme orprotocol. Congestion exposure may use and be built upon ECN. Congestionexposure may provide a mechanism that allows a sender to inform thenetwork about remaining path congestion that is expected to beencountered by packets. In ECN the network may signal congestion by ECNmarking packets or by dropping packets and the receiver may pass thisinformation back to the sender as feedback. Congestion exposure buildson this by allowing the sender to relay or insert expected remainingpath congestion information back into the network to inform the networkof this expected congestion. The expected rest-of-path congestioninformation may be based on or derived from congestion previouslyencountered by previous packets in the same flow as indicated in the ECNfeedback. The network nodes may use this information to estimate howmuch congestion the flow is likely to cause by sending or forwarding thetraffic and may make decisions based on this information. Congestionexposure may provide the information and ability to make flowsaccountable for the congestion that they cause, or allow to be caused,and may help to manage congestion.

Re-ECN is a known implementation of congestion exposure. Re-ECN isdescribed in the Transport Area Working Group Internet Engineering TaskForce (IETF) Internet-Draft entitled “Re-ECN: Adding Accountability forCausing Congestion to TCP/IP,” by Bob Briscoe et al., dated Oct. 25,2010, pages 1-51. The re-ECN protocol provides a field in each packet sothat, as the packet crosses any interface in an internetwork, it carriesa truthful prediction of congestion on the remainder of its path.

SUMMARY

In one aspect, a method for localized congestion exposure within a localloop in a cellular network performed by a localized congestion exposurereceiver node of the local loop includes several steps. In one step,downlink packets destined for a downstream user device are received. Thedownlink packets have headers that indicate a level of congestionexperienced by the downlink packets. The headers also indicate a levelof expected downstream congestion declared by an upstream node. Inanother step, the downlink packets are forwarded to the downstream userdevice through a wireless connection. In a further step, packets thathave feedback indicative of the level of congestion experienced by thedownlink packets, and any congestion experienced within the localizedcongestion exposure receiver node, are sent upstream. One possibleadvantage is that localized congestion exposure may be achieved withinthe local loop in the cellular network whether or not congestionexposure is supported outside of the local loop, to allow congestion tobe managed within the local loop.

In another aspect, a localized congestion exposure receiver nodeconfigured for localized congestion exposure within a local loop in acellular network. The receiver node includes a first interfaceconfigured to receive downlink packets destined for a downstream userdevice. The downlink packets have headers that indicate a level ofcongestion experienced by the downlink packets. The headers alsoindicate a level of expected downstream congestion declared by anupstream node. The receiver node also has a second interface configuredto send the downlink packets to the downstream user device through awireless connection. The receiver node also includes a feedback inserterto insert feedback indicative of the level of congestion experienced bythe downlink packets, and any congestion experienced within thelocalized congestion exposure receiver node, into packets that are sentupstream through the first interface. One possible advantage is thatlocalized congestion exposure may be achieved within the local loop inthe cellular network whether or not congestion exposure is supportedoutside of the local loop, to allow congestion to be managed within thelocal loop.

In a further aspect, a method for localized congestion exposure within alocal loop in a cellular network performed by a localized congestionexposure sender node of the local loop includes several steps. In onestep, downlink packets destined for a downstream user device arereceived. In another step, packets having feedback indicating acongestion level are received from a downstream node of the cellularnetwork. In a further step, a declaration of an expected downstreamcongestion level is inserted into headers of the received downlinkpackets. In another step, the downlink packets having the declaration ofthe expected downstream congestion level inserted into the headersthereof are forwarded toward the downstream user device. One possibleadvantage is that localized congestion exposure may be achieved withinthe local loop in the cellular network whether or not congestionexposure is supported outside of the local loop, to allow congestion tobe managed within the local loop.

In yet another aspect, a localized congestion exposure sender nodeconfigured for localized congestion exposure within a local loop in acellular network. The localized congestion exposure sender node is to bedeployed in the local loop between a base station and Internet. Thesender node has a first interface configured to receive downlink packetsdestined for a downstream user device. The sender node also has a secondinterface configured to receive packets having feedback indicating acongestion level from a downstream node of the cellular network. Acongestion exposure inserter of the sender node is configured to inserta declaration of an expected downstream congestion level into headers ofthe received downlink packets. The sender node is configured to forwardthe downlink packets having the declaration of the expected downstreamcongestion level inserted into the headers thereof toward the downstreamuser device. One possible advantage is that localized congestionexposure may be achieved within the local loop in the cellular networkwhether or not congestion exposure is supported outside of the localloop, to allow congestion to be managed within the local loop.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 illustrates an example embodiment of localized congestionexposure in a 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) cellular network.

FIG. 2 is an example embodiment of outer and inner IP headers.

FIG. 3 is a block flow diagram of an example embodiment of a method forlocalized congestion exposure within a local loop in a cellular networkperformed by a localized congestion exposure receiver node (e.g., aneNodeB or other base station) of the local loop.

FIG. 4 is a block diagram illustrating an example embodiment of a reportformat for feedback.

FIG. 5 is a block diagram of an example embodiment of a localizedcongestion exposure receiver node (e.g., an eNodeB or other basestation) configured for localized congestion exposure within a localloop in a cellular network.

FIG. 6 is a block flow diagram of an example embodiment of a method forlocalized congestion exposure within a local loop in a cellular networkperformed by a localized congestion exposure sender node (e.g., agateway) of the local loop.

FIG. 7 is a block diagram of an example embodiment of a localizedcongestion exposure sender node (e.g., a gateway) configured forlocalized congestion exposure within a local loop in a cellular network.

FIG. 8 illustrates a second example embodiment of localized congestionexposure in a 3GPP LTE cellular network, in which ECN is supportedend-to-end.

FIG. 9 illustrates a third example embodiment of localized congestionexposure in a 3GPP LTE cellular network, in which both ECN andcongestion exposure are supported end-to-end.

FIG. 10 illustrates an example embodiment of localized congestionexposure in a 3GPP LTE cellular network for an upload scenario in whichpackets are uploaded from user equipment to the Internet.

DESCRIPTION OF EMBODIMENTS

The following description describes methods and apparatus for localizedcongestion exposure. In the following description, numerous specificdetails are set forth, such as particular network configurations,particular types of congestion information, particular fields withinheaders, and the like. However, it is understood that embodiments of theinvention may be practiced without these specific details. In otherinstances, well-known circuits, structures and techniques have not beenshown in detail in order not to obscure the understanding of thisdescription.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

Currently, the use of ECN, re-ECN, and congestion exposure is verylimited. A significant contributing factor is that these congestionavoidance schemes tend to be very challenging to employ end-to-end froma receiver end terminal to a sender end terminal across a public networksuch as the Internet. One reason it is difficult to achieve fullend-to-end deployment is that it typically involves modifying thereceiver and sender end terminals, such as cell phones, smart phones,laptops, servers, routers, switches, etc., so that they support thesecongestion avoidance schemes. For example, the sender needs to be ableto insert the feedback back into the network in congestion exposure.This typically involves support by, for example, the transmissioncontrol protocol (TCP)/Internet Protocol (IP) stacks in the operatingsystem of interest (e.g., Linux, Windows, etc. for servers and Android,Windows mobile, etc. for cell phones). However, there are a large numberof different manufacturers/vendors of such end terminals, and it ischallenging to convince all of these manufacturers/vendors to agree tohave the end terminals support these congestion avoidance schemes.

Another reason that it is difficult to achieve full end-to-enddeployment is that the manufacturers of the routers in the Internet tendto be reluctant to modify their routers to support ECN and congestionexposure. In order to support ECN and congestion exposure, routers alongthe path, especially on the bottleneck links, should mark the ECN fieldto indicate congestion, but if they do not then ECN may not work aswell. Moreover, it is common to have middleboxes, such as firewalls orintrusion detection systems (IDS), set up along the path. The congestionexposure framework should be such that these middleboxes do not clearECN marks or the congestion exposure information. This is hard toguarantee, since the middleboxes may belong to different networkmanagement entities. For the above reasons it is reasonable to assumethat deployment of congestion exposure that works end-to-end will bechallenging and will take a significant amount of time.

Methods and apparatus for localized congestion exposure are disclosedherein. The term localized congestion exposure is intended to encompasslocalized re-ECN. For example, an embodiment of localized re-ECN is alsoan embodiment of localized congestion exposure. In the localizedcongestion exposure, the congestion exposure information is localizedrather than only end-to-end. An advantage of the localized congestionexposure is the local property. The localized congestion exposure isuseful for instance when it is not possible or practical to enablecongestion exposure end-to-end and can, for instance, be deployed alonga specific path. Previous proposals on congestion exposure are allpurely end-to-end base, which as discussed above involves modificationto the end hosts to support congestion exposure. This may create adeployment burden to the adoption of congestion exposure protocol. Thenew localized congestion exposure removes such restrictions. Localizedcongestion exposure can achieve fair resource control without anymodification to the end hosts. Since the number of infrastructure nodesin localized congestion exposure is typically much smaller than thenumber of end hosts, and the infrastructure nodes may be under thecontrol of the same network administration entity, the deploymentoverhead may be significantly reduced. In addition, end-to-endcongestion exposure may be ineffective because ECN capability may bereset or IPv6 extension headers may be removed by middleboxes along thepath, but this problem may be avoided or at least more manageable inlocalized congestion exposure. In addition the local congestion exposureapproach disclosed herein is incrementally deployable, and may serve asa natural stepping stone towards end-to-end congestion exposure once itbecomes widely deployed.

FIG. 1 illustrates an example embodiment of localized congestionexposure in a 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) cellular network 100. The localized congestion exposureis practical and useful in LTE networks. In this example embodiment,neither ECN nor congestion exposure are supported at the end host. Thisis likely to be the dominant case initially.

The illustration depicts an example LTE architecture cellular network100 and data plane path for data traffic in the 3GPP LTE cellularnetwork. The eNodeB 103 is the name given to the LTE network basestation. It is to be appreciated that there may be other base stations(not shown) in the network. The eNodeB is used for realizing the actualwireless connections 102 between user devices or equipment 101 and thenetwork. The user data payload (the Internet Protocol (IP) packets)from/to the user equipment is handled by two logical nodes called theServing Gateway (Serving-GW or S-GW) 105 and the Packet Data NetworkGateway (PDN-GW) 106. The Serving-GW terminates an S1-U user planeinterface towards the eNodeB. The Serving-GW also buffers downlink IPpackets destined for user equipment 101 that happen to be in idle mode.The PDN-GW serves as a gateway towards Internet 108. The PDN-GW is thepoint of interconnect to external IP networks (e.g., the Internet)through an SGi interface. The PDN-GW also includes functionality for IPaddress allocation, charging, packet filtering, and policy-based controlof flows. The S-GW and PDN-GW are logically separated entities accordingto LTE, although it is to be appreciated that they may be physicallydeployed on either one or more physical systems. The S-GW and the PDN-GWare subcomponents of System Architecture Evolution (SAE) whichrepresents the core network architecture of LTE. The main component orcore of SAE is known as the SAE core or Evolved Packet Core (EPC). Theillustrated LTE architecture also includes a first router 104 betweenthe eNodeB and the S-GW and a second router 107 connecting the PDN-GW tothe Internet. It is to be appreciated that the network may include moreor less routers (e.g., more routers between the base station and theS-GW, one or more routers between the S-GW and the PDN-GW, more routersbetween the PDN-GW and internet, etc. The eNodeB, the first router 104,the S-GW, the PDN-GW are commonly owned and operated by the same networkoperator entity. The Internet includes routers, only a third router 109of which is illustrated for simplicity. A source or server 110 iscoupled to the cellular network across the Internet.

Taking this example LTE infrastructure as shown in FIG. 1, congestionmay occur at multiple places, such as eNodeB (most likely), S-GW,PDN-GW, and routers and switches along the path. Recently there has beena significant increase in data traffic in cellular networks due in partto video download, etc. In a download scenario, the user device (e.g., acell phone) 101 downloads content (e.g. a streamed movie) from a serveror source 110. In the illustration, a download scenario is exemplified,since the traffic volume on the downloading direction typically is muchlarger than that on the upstream direction. As a result, the downloadscenarios are more likely to cause congestion due to the larger trafficvolume, in which case the localized congestion exposure has morebenefit. As will be described further below, a similar setup can be donefor upload scenarios, although the benefits of localized congestionexposure may not be as apparent, unless or until the traffic volume onthe upload direction increases to a point that causes congestion (e.g.,if the user equipment uses videotelephony, sends video, or otherwisesends large amounts of data).

The localized congestion exposure framework is implemented in the LTEinfrastructure nodes, for example eNodeB, S-GW, and PDN-GW. In theillustration, the path between the eNodeB (base station) node and thePDN-GW node is exemplified, although the scope of the invention is notlimited to this particular path. In this case localized congestionexposure is deployed along the path between the PDN-GW and the eNodeB.This means that the congestion exposure loop only runs locally betweenthe PDN-GW and the eNodeB nodes. Neither ECN nor congestion exposureneeds to be supported outside of this loop. However, embodiments of theinvention will work in cases when ECN and congestion exposure aredeployed in the end-to-end path.

In the illustrated embodiment, the base station or eNodeB serves as thecongestion exposure receiver node and the PDN-GW serves as thecongestion exposure sender node. Nodes along the path between the PDN-GWand the eNodeB (e.g., as shown the S-GW, the eNodeB, and the firstrouter 104 between the S-GW and the eNodeB) may mark the ECN bit ofpackets to indicate congestion is experienced (“Mark ECN bit 113”). Thebase station or eNodeB may provide feedback regarding the ECN markingsin the packets to indicate of the level of congestion experienced by thepackets (“Feedback ECN Marking 111”). The PDN-GW may receive thefeedback and re-insert feedback or congestion information back into thenetwork as congestion exposure or re-ECN information (“Re-insertfeedback 112”). Congestion exposure encodes congestion notification intodata headers. Packets sent from the PDN-GW may carry a truthfulprediction about the congestion condition of the remainder of theirpath. The re-feedback may include both an indication of the proportionof packets marked this window as nodes perform ECN marking, and anindication of the proportion of packets marked the previous window.Advantageously, localized congestion exposure may be achieved within thelocal loop in the cellular network whether or not congestion exposure issupported outside of the local loop. One potential advantage is that oneor more nodes of the cellular network may use the localized congestionexposure information, for example, to one or more of allocate or controlresources, drop packets, find malicious flows, find misbehaving users,stop malicious traffic from consuming more network resources, and/orotherwise hold flows, users, customers and data sources, accountable forthe congestion they cause downstream.

In the LTE cellular network, packets between the PDN-GW node and theeNodeB node (the LTE network base station) are tunneled over GeneralPacket Radio Service (GPRS) Tunneling Protocol (GTP). GTP is thedelivery protocol to deliver data for a payload protocol. GTP is atunneling protocol over user datagram protocol (UDP)/Internet Protocol(IP). GTP may be used with either UDP or TCP. UDP and TCP are at thetransport layer or level. The transport layer or level is at a highernetwork layer or level than IP. IP is at the Internet layer or level. Inaddition, GTP is logically higher than UDP. A GTP path is identified ineach node with an IP address and a UDP port number. The GTP protocolincludes both for the data traffic (GTP-U) and the control traffic(GTP-C). That is, user plane traffic or path between PDN-GW and eNodeBis tunneled over GTP-U (U for user plane) tunnels, and a separate GTP-Cprotocol exists for the control signaling. This is very different fromthe end-to-end path on the Internet where the packet forwarding isperformed at the IP level.

In the illustrated embodiment of the invention, congestion exposure isdeployed along the GTP-U path between PDN-GW and eNodeB. That is, theGTP-U path supports congestion exposure. Implementing the localizedcongestion exposure at the higher level of GTP facilitatesimplementation. These tunneling protocols give the operator a largedegree of flexibility to control the congestion mechanism incorporatedwith the GTP protocols. Existing GTP tunnel is a UDP based tunnelingprotocol without any congestion avoidance mechanisms. Support for ECNover this path is currently unspecified but is relativelystraightforward. Reference may be made to ECN for generic IP over IPtunneling.

FIG. 2 is an example embodiment of an outer IP header 215 and an innerIP header 216. The outer IP header has outer congestion encountered orexperienced markings (CEo) 217. The inner IP header has inner congestionencountered or experienced markings (CEi) 218. Implementing support forECN in the GTP-U tunnels may include the outer IP header being indicatedas ECN capable. Such ECN marking support on GTP tunneling is believed tobe new. In one aspect, ECN-CE markings in the outer IP header may not becopied to the inner IP header at tunnel egress if the inner header isnot ECN capable. In one aspect, the GTP-U protocol may use the optionalsequence number to make the feedback reports reliable.

FIG. 3 is a block flow diagram of an example embodiment of a method 320for localized congestion exposure within a local loop in a cellularnetwork performed by a localized congestion exposure receiver node ofthe local loop. In one embodiment, the localized congestion exposurereceiver node may be an eNodeB or other base station.

The method includes receiving downlink packets destined for a downstreamuser device, at block 321. The downlink packets have headers thatindicate a level of congestion experienced by the downlink packets(e.g., ECN-CE markings or other indications that congestion wasencountered or experienced). The headers also indicate a level ofexpected downstream congestion declared by an upstream node (e.g.,re-ECN information or other congestion exposure information).

In one embodiment, the downlink packets as received may have outerheaders that indicate ECN capable transport and inner headers thatindicate not ECN capable transport. In one embodiment, the downlinkpackets may be received through a tunnel, which is not an IP over IPtunnel, and an outer header of the downlink packets as received mayindicate ECN capable transport. In one aspect, the tunnel may be aGeneral Packet Radio Service (GPRS) Tunneling Protocol (GTP) tunnel, andthe level of the expected downstream congestion declared by the upstreamnode may be indicated in GTP headers of the downlink packets receivedthrough the GTP tunnel.

The method includes forwarding the downlink packets to the downstreamuser device through a wireless connection, at block 322. In oneembodiment, for example when the downstream user device does not supportcongestion exposure, the downlink packets forwarded may not indicate thelevel of expected downstream congestion declared by the upstream node.

The method also includes sending packets upstream that have feedbackindicative of the level of congestion experienced by the downlinkpackets and any congestion experienced within the localized congestionexposure receiver node, at block 323. In this case, the eNodeB, basestation, or other node serves as the receiver node in the normalcongestion exposure/ECN deployment.

The eNodeB may collect the ECN-CE marks and provide feedback to thePDN-GW. Moreover, the schedulers in eNodeB are likely points wherecongestion may be encountered. Other points may be a queue on the RadioLink Control (RLC) layer with active queue management (AQM) algorithm.As ECN is not enabled for the inner IP header, packets may be dropped asa congestion indication. This congestion information may also be fedback to the PDN-GW. In one aspect, this congestion information may becombined (e.g., logically ORed) with the ECN-CE marks on outer IP header(CEi∥CEo in FIG. 2). A possible report interval may be once every roundtrip time (RTT) or perhaps more seldom. In one embodiment, the feedbackmay be provided in-line, for example through ECN code-point bits spreadacross multiple or many packets.

The feedback may include various different types of information. FIG. 4is a block diagram illustrating an example embodiment of a report format424 for feedback. The report format may contain one or more of thefollowing types of information:

(a) sequence number of last received packet 425;

(b) total number of packets received (by eNodeB or base station) 426;

(c) total number of packets dropped by eNodeB or base station (e.g., inscheduler or AQM) 427;

(d) total number of packets ECN-CE marked by eNodeB or base station(e.g., in scheduler or AQM) 428;

(e) total number of packets dropped by nodes before eNodeB (GTP-Utunneled packets) 429;

(f) total number of packets ECN-CE marked by nodes before eNodeB or basestation (GTP-U tunneled packets) 430;

(g) list of marked and/or dropped packets 431, which may be useful forcomputation of congestion volume (sum of sizes of marked or droppedpackets). Congestion volume may represent the volume of the packets thatare marked, and may be computed as the accumulated packet size of allmarked packets, this can be put in relation to the total traffic volume,the congestion volume is then expressed as a percentage. Congestionvolume can be computed per flow, per user, per aggregate of flows, etc.Moreover the congestion volume can be computed per time or as anaccumulated metric.

Accordingly, the eNodeB or base station may provide the feedback andserve as the receiver node in the congestion exposure/ECN deployment.Advantageously, various of the types of information listed above, whichmay be readily known by the eNodeB or base station, may not be known orreadily known by a cell phone or other user equipment. Some of theinformation is privy to, internal to, or only known by the base station.For example, the base station may typically know or be able to figureout the types of information listed for (b), (c), (d), (e), or (f), butthe cell phone or other user equipment may not be able to know or figureout these types of information. For example, considering the types ofinformation listed for (c) and (e), the base station may know or be ableto figure out the total number of packets it dropped and the totalnumber of packets dropped by nodes before the base station (e.g., byanalyzing packet sequence numbers to see which ones are missing).However, the cell phone or other user equipment may only be able to knowor figure out the total number of packets dropped prior to the cellphone, but may not be able to differentiate which of these packets weredropped prior to the base station versus which of these packets weredropped by the base station.

The illustrated report format is only one example embodiment. Aspreviously mentioned, the report format may contain one or more of thesetypes of information (i.e., not all of this information is required).Moreover, alternate embodiments of report formats may include othertypes of information besides just those listed above. Naturally, theorder/arrangement of the various types of information is not requiredand may optionally be rearranged.

FIG. 5 is a block diagram of an example embodiment of a localizedcongestion exposure receiver node 503 configured for localizedcongestion exposure within a local loop in a cellular network. In oneembodiment, the localized congestion exposure receiver node may be aneNodeB or other base station.

The localized congestion exposure receiver node has a first interface535 configured to receive downlink packets 536 destined for a downstreamuser device over a connection 537. The downlink packets having headersthat indicate a level of congestion experienced by the downlink packets(e.g., ECN-CE markings or other indications that congestion wasencountered or experienced). The headers also indicate a level ofexpected downstream congestion declared by an upstream node (e.g.,re-ECN information or other congestion exposure information).

In one embodiment, the downlink packets as received may have outerheaders that indicate ECN capable transport and inner headers thatindicate not ECN capable transport. In one embodiment, the downlinkpackets may be received through a tunnel, which is not an IP over IPtunnel, and an outer header of the downlink packets as received mayindicate ECN capable transport. In one aspect, the tunnel may be aGeneral Packet Radio Service (GPRS) Tunneling Protocol (GTP) tunnel, andthe level of the expected downstream congestion declared by the upstreamnode may be indicated in GTP and/or outer IP headers of the downlinkpackets received through the GTP tunnel. In one aspect, the level ofexpected downstream congestion may be conveyed in IP header extensions.In another aspect, the level of expected downstream congestion may beconveyed using bits from a flow label field in an IPv6 header.

The localized congestion exposure receiver node has a second interface538 configured to send the downlink packets 539 to the downstream userdevice through a wireless connection 540. In one embodiment, for examplewhen the downstream user device does not support congestion exposure,the forwarded downlink packets may not indicate the level of expecteddownstream congestion declared by the upstream node.

The localized congestion exposure receiver node has a feedback inserter541 to insert feedback indicating the level of congestion experienced bythe downlink packets into packets 542 that are sent upstream through thefirst interface. The feedback inserter may insert feedback including anyone or more of the types of information shown in FIG. 4. The feedbackinserter may be implemented in software, firmware, hardware (e.g.,circuitry) or a combination.

In one embodiment, the localized congestion exposure loop may include adropper 543 (e.g., an edge egress dropper) or other guard at the egressto prevent or discourage understatement of expected downstreamcongestion. In one aspect, the dropper or guard may be introduced at thelast network egress, although this is not required.

The localized congestion exposure, as in the re-ECN framework, maydefine positive or negative flows, meaning flows where the movingaverage of the downstream congestion metric is persistently positive ornegative. A negative flow is one having more congestion experienced orencountered (CE) marked packets than the sender declared or claims tocause. In positive flows the claimed or declared congestion is more thanthe actual level. The notion of a negative flow or metric may arisebecause it is derived by subtracting the real congestion level from theclaimed or declared congestion level.

The guard or dropper 543 may drop packets in flows that become negativedownstream congestion, i.e. the congestion caused in reality is higherthan that claimed or declared. As traffic leaves the last network nodebefore the receiver, the fraction of positive octets in a flow shouldmatch the fraction of negative octets introduced by congestion marking,leaving a balance of zero. When positive, the dropper may take noaction, meaning that the source is slower than it has to. The router ordropper may drop packets in negative flows, for example, to ensurefairness. Advantageously, this may help to ensure both that congestionis declared honestly and that the sender's rate responds appropriately.Moreover, the dropper may optionally be omitted, for example if the pathbetween the PDN-GW and the eNodeB is trusted.

The localized congestion exposure approach introduces the necessaryincentives (e.g., whip and carrot mechanisms) for sources to behave insuch a way that excessive congestion can be avoided. This may result ina more stable Internet experience for all users. In one aspect, thelocalized congestion exposure approach may be net-neutral such that itdoes not make judgments based on type of traffic (e.g., video on demand(VoD), peer-to-peer (p2p), etc.), but instead the localized congestionexposure approach does only care for the amount of congestion that iscaused, although the scope of the invention is not limited in thisrespect.

Referring again to FIG. 5, in one embodiment, the base station or eNodeBmay have an ECN marker or other congestion experienced/encounteredmarker 544. The ECN marker may mark the ECN field of packets (e.g., markECN-CE). Alternatively, in another embodiment, the base station oreNodeB may not necessarily have an ECN marker. For example, the basestation or eNodeB may know which packets it would ECN mark, and canincorporate such packets into the feedback, without ECN marking them.

In one embodiment, the example embodiment of the localized congestionexposure receiver node of FIG. 5 may perform the example embodiment ofthe operations and method of FIG. 3. However, it should be understoodthat the operations and method of FIG. 3 can be performed by alternateembodiments of the invention other than those discussed with referenceto FIG. 5. Further, the localized congestion exposure receiver node ofFIG. 5 can perform other operations and methods different than those ofFIG. 3.

FIG. 6 is a block flow diagram of an example embodiment of a method 648for localized congestion exposure within a local loop in a cellularnetwork performed by a localized congestion exposure sender node of thelocal loop. In one embodiment, the localized congestion exposure sendernode may be a cellular network gateway (e.g., a PDN-GW or an S-GW).Alternatively, the localized congestion exposure sender node may be arouter.

The method includes receiving downlink packets destined for a downstreamuser device, at block 649. In one embodiment, for example when an endterminal does not support congestion exposure, the downlink packets asreceived may not have a declaration of expected downstream congestion(e.g., there may be no re-ECN information or other congestion exposureinformation). In one embodiment, the downlink packets as received mayhave headers that indicate not ECN capable transport.

The method includes receiving packets having feedback indicating acongestion level from a downstream node of the cellular network, atblock 650. In one embodiment, the feedback may include any one or moreof the types of information shown in FIG. 4. Possible examples of suchinformation may include one or more of total number of packets droppedby the base station, total number of packets dropped by nodes before thebase station, total number of packets ECN-CE marked by the base station,total number of packets ECN-CE marked by nodes before the base station,etc.

The method includes inserting a declaration of an expected downstreamcongestion level into headers of the received downlink packets, at block651. In one embodiment, the declaration or claim of the expecteddownstream congestion information may include re-ECN information orother congestion exposure information. It is to be appreciated that thescope of the invention is not limited to the declared or claimedexpected downstream congestion level accurately corresponding to theactual level (e.g., the declared or claimed congestion level may befalse without limitation to the scope of the invention).

The method includes forwarding the downlink packets having thedeclaration of the expected downstream congestion level inserted intothe headers thereof toward the downstream user device, at block 652. Inone embodiment, the downlink packets may be forwarded through a tunnel,which is not an IP over IP tunnel, and an outer header of the downlinkpackets as forwarded may indicate ECN capable transport. In one aspect,the tunnel may be a GTP tunnel, and the declaration of the expecteddownstream congestion level may be indicated in GTP headers of thedownlink packets. In one embodiment, the PDN-GW can re-insert thecongestion information into the GTP-U headers.

FIG. 7 is a block diagram of an example embodiment of a localizedcongestion exposure sender node 706 configured for localized congestionexposure within a local loop in a cellular network. The localizedcongestion exposure sender node is to be deployed in the local loopbetween a base station and Internet. In one embodiment, the localizedcongestion exposure sender node may be a cellular network gateway (e.g.,a PDN-GW or an S-GW). Alternatively, the localized congestion exposuresender node may be a router.

The localized congestion exposure sender node has a first interface 755configured to receive downlink packets 756 destined for a downstreamuser device over a first connection 757. In one embodiment, for examplewhen an end terminal does not support congestion exposure, the interfacemay receive downlink packets that do not have a declaration of expecteddownstream congestion (e.g., there may be no re-ECN information or othercongestion exposure information). In one embodiment, the interface mayreceive downlink packets that have headers that indicate not ECN capabletransport.

The localized congestion exposure sender node has a second interface 758configured to receive packets 759 having feedback indicating acongestion level from a downstream node of the cellular network over asecond connection 760. In one embodiment, the second interface mayreceive feedback that may include any one or more of the types ofinformation shown in FIG. 4.

The localized congestion exposure sender node has a congestion exposureinserter 761 configured to insert a declaration of an expecteddownstream congestion level into headers of the received downlinkpackets 762. In one embodiment, the congestion exposure inserter mayinsert a declaration or claim of the expected downstream congestioninformation that includes re-ECN information or other congestionexposure information. The congestion exposure inserter may beimplemented in software, firmware, hardware (e.g., circuitry), or acombination thereof. The sender node is configured to forward thedownlink packets having the declaration of the expected downstreamcongestion level inserted into the headers thereof toward the downstreamuser device.

To ensure honest marking, a few entities may be included in the networkto help to ensure the correct behavior. One entity is source congestioncontrol. The sender may throttle its rate as downstream congestionincreases, with some version of TCP-friendly congestion response. Aspreviously discussed, the cellular network may have an edge egressdropper. Moreover, in one embodiment, the cellular network may have aningress policer. Re-ECN and congestion exposure protocols ensure thatpackets carry information about their own expected downstreamcongestion. In one embodiment, a PDN-GW or access router can deploy apolicer at its ingress to check that a source is complying with whatevercongestion control it should be using. The policer may drop packets orstop flows for aggressive flows/users at the ingress to help avoidwasting downstream resources. As shown, in one embodiment, the PDN-GWmay optionally have a policer 763. Alternatively, another component(e.g., an access router or first hop router connecting the PDN-GW to theInternet) may have such a policer.

This policing (e.g., by the PDN-GW) can be performed based on either perflow or a per customer basis. By way of example, to ensure that a flow,a user, or a set of customers doesn't generate more congestion in thenetwork than its due share, a modified bulk token-bucket can bemaintained to allocate the resources gradually over time. Tokens mayrepresent the amount of congestion each user allows to consume in thenetwork. The modified bulk token-bucket may have parameters such as theinitial token level, the filling rate, and the bucket depth. All trafficfrom a user over the lifetime of their subscription may be policed inthe same token bucket. Such a modified bulk token bucket is notrequired. Alternatively, other approaches for representing the amount ofcongestion each user is allowed to consume in the network and/orallocating network resources may be used instead, such as, for example,various types of moving averages or approaches known for re-ECN orcongestion exposure.

The PDN-GW or policer can apply policing on flows depending on theoperator preference. For instance the PDN-GW or policer may drop packetsat the ingress for sources that cause more than 1% ECN rate orcongestion volume, for example. The ECN rate may represent the number ofECN-CE marked packets divided by the total number packets. This value istypically computed over a sliding window, for example over the last 100packets. As another example, a more friendly action is to providecontent providers with feedback on how much their services congest thenetworks.

Referring again to FIG. 7, the PDN-GW also includes an optional feedbackanalyzer 764 to analyze the feedback. The feedback analyzer may beimplemented in hardware, software, firmware, or a combination thereof.The PDN-GW gets the feedback or congestion information (e.g., the typesof information shown in FIG. 4) from the base stations or eNodeBs. ThePDN-GW or the feedback analyzer can, based on this information detect orfind one or more of the following:

(a) find malicious flows;

(b) find misbehaving users;

(c) find aggressive sources of traffic; and/or

(d) more easily find overloaded spots in the network.

The detection can be implemented by keeping the statistical value of ECNmarked packets. As an example of the possible actions, the PDN-GW cansee if several users are connected to one particular source (e.g. apopular video on demand (VoD) service) and that these flows all case atoo high ECN-rate. It is then likely that the source need to improve itscongestion control algorithms. Another interesting case is if one usergets data from many sources and shows a total high ECN-rate. It is thenpossible that the user is subject to a distributed denial-of-service(DDoS) attack. These two scenarios can both be detected by monitoringthe ECN marking rate in the PDN-GW.

If we take a download use case, it may be tempting to implement ECN andsome kind of policing only in eNodeB, which is one possible option foran embodiment of the invention. However, one potential drawback to doingso is that it is then difficult to know if a specific source isresponsible for congestion (e.g., denial-of-service (DoS) ornon-responsive congestion control algorithms in source). What is betteris for the eNodeB to feedback the ECN marks to the PDN-GW, so the PDN-GWcan perform better analysis to localize misbehaving sources based onbulk data, and then make better policing decisions. Further, enforcingthe policing decisions at the ingress hop, for example the PDN-GW, is anefficient way to stop malicious traffic from consuming more networkresources.

In one embodiment, the S-GW and PDN-GW (e.g., the outgoing queue) may beECN capable. For example, they may each have an ECN marker that is ableto set ECN-CE to indicate congestion encountered or experienced on theouter IP header. In one aspect, they may mark packets with probabilitydepending on an average queue size. To encode the congestion level tothe packet, we need ECN enabled routers which mark the packets whenevercongestion occurs. The routers along the path may also be ECN capable.In one aspect, this can be implemented together with random earlydetection (RED) which is widely supported in commercial routers. Asshown, the illustrated sender node 706 has an optional ECN marker orother congestion exposure inserter 765. Alternatively, as shown in FIG.1, the PDN-GW may be outside the bracket and need not necessarily ECNmark packets, but rather this may be performed by other nodes (e.g.,S-GW, routers, etc.).

In one embodiment, the example embodiment of the localized congestionexposure receiver node of FIG. 7 may perform the example embodiment ofthe operations and method of FIG. 6. However, it should be understoodthat the operations and method of FIG. 6 can be performed by alternateembodiments of the invention other than those discussed with referenceto FIG. 7. Further, the localized congestion exposure receiver node ofFIG. 7 can perform other operations and methods different than those ofFIG. 6.

FIG. 8 illustrates a second example embodiment of localized congestionexposure in a 3GPP LTE cellular network 800 in which ECN is supportedend-to-end. ECN is enabled on both end points (e.g., user equipment 801and a source 810). Routers of the Internet may also support ECN.

The illustrated LTE cellular network includes a user equipment 801, aneNodeB 803 having a wireless connection 802 to the user equipment, afirst router 804, a S-GW 805, a PDN-GW 806. The LTE cellular network maybe as previously described and may have any of the variations previouslydescribed. Also shown are Internet 808, a second router 807, a thirdrouter 809, and a source 810.

The eNodeB is ECN enabled. The source is also ECN enabled. The eNodeBprovides feedback (“Feedback ECN Marking 811”) to the ECN enabledsource. The eNodeB, the first router, the S-GW, the PDN-GW, and routersof the Internet may perform ECN marking (“Mark ECN bit 813”). The PDN-GWmay perform policing. The PDN-GW may provide congestion exposureinformation (“Re-insert feedback 812”).

In one embodiment, localized congestion exposure in the LTE cellularnetwork may have primarily an interest to protect the traffic that goesfrom PDN-GW to eNodeB (or UE). For this reason, in one aspect, onlyECN-CE marking that occurs within this local network may be considered.Policing or a policer at the PDN-GW ingress (or other localizedcongestion exposure sender) may therefore subtract the incoming measuredECN rate (at the PDN-GW ingress) from the fed back ECN-rate from theeNodeB or base station (or other localized congestion exposurereceiver). This will give a measure of how much a flow congests alongthe downstream path from PDN-GW.

FIG. 9 illustrates a third example embodiment of localized congestionexposure in a 3GPP LTE cellular network 900 in which both ECN andcongestion exposure are supported end-to-end. ECN is enabled on both endpoints (e.g., user equipment 901 and a source 910). Congestion exposureis also enabled on both end points. Routers of the Internet may alsosupport ECN and congestion exposure.

The illustrated LTE cellular network includes a user equipment 901, aneNodeB 903 having a wireless connection 902 to the user equipment, afirst router 904, a S-GW 905, a PDN-GW 906. The LTE cellular network maybe as previously described and may have any of the variations previouslydescribed. Also shown are Internet 908, a second router 907, a thirdrouter 909, and a source 910.

The ECN enabled user equipment or device provides feedback (“FeedbackECN Marking”) to the ECN enabled source. The ECN enabled source mayprovide congestion exposure information (“Re-insert feedback”) back intothe network and it may go all the way to the ECN enabled user equipmentor device. The eNodeB, the first router, the S-GW, the PDN-GW, androuters of the Internet may perform ECN marking (“Mark ECN bit”).

The PDN-GW may have a policer. The eNodeB may have a dropper and may actas an edge egress dropper. The end-to-end path may be establishedbetween user equipment (UE) and data provider servers, where the IPconnection is established on top of an overlay path on top of eNodeB,S-GW, etc. The policer can be deployed on the first hop of the pathunder mobile operator's control, i.e. the PDN-GW. The dropper isdeployed at the egress of the path, in this example, the last hop inmobile backhaul, the eNodeB. It can also be deployed on the S-GW,depending on the resource contention concerns in the network, or on thelast hop before eNodeB, for example.

Example embodiments of localized congestion exposure have been shown anddescribed for 3GPP LTE cellular networks. As used herein, the term LTEis intended to encompass future versions and releases of LTE, forexample LTE Advanced, 4G, etc. Moreover, embodiments of localizedcongestion exposure methods and apparatus as disclosed herein may beused in future non-LTE cellular, such as successors to 3G, LTE, and 4Gcellular networks.

Advantageously, localized congestion exposure may be achieved within thelocal loop in the cellular network whether or not congestion exposure issupported outside of the local loop. Advantageously, one or more nodesof the cellular network may use the localized congestion exposureinformation to one or more of, allocate or control resources, droppackets, find malicious flows, find misbehaving users, stop malicioustraffic from consuming more network resources, etc.

Download scenarios, in which packets are downloaded to user equipmentfrom the Internet, have been exemplified, due to the large volume oftraffic presently experienced in the download direction, for example dueto video downloads to cell phones. However, a large volume of trafficmay also be experienced in the upload direction, in which packets areuploaded from user equipment (e.g., cell phones) to the Internet inroute to other user equipment or servers. For example, this may be thecase for videotelephony, or when cell phones or other user equipmentupload video or other large amounts of data.

FIG. 10 illustrates an example embodiment of localized congestionexposure in a 3GPP LTE cellular network for an upload scenario in whichpackets are uploaded from user equipment to the Internet. Localizedcongestion exposure in a case where the end points do not supportcongestion exposure or ECN is used for purposes of illustration,although other embodiments apply to the scenarios of FIGS. 8-9.

The illustration shows a LTE cellular network 1000 including a userequipment 1001, an eNodeB 1003 having a wireless connection 1002 to theuser equipment, a first router 1004, an S-GW 1005, a PDN-GW 1006. TheLTE cellular network may be as previously described and may have any ofthe variations previously described. Also shown are Internet 1008, asecond router 1007, a third router 1009, and a source 1010.

In this upload scenario, the PDN-GW is the congestion exposure receivernode and the eNodeB is the congestion exposure sender node.Alternatively, another node (e.g., the S-GW) may be the congestionexposure receiver node, and another node (e.g., the first router 1104)may be the congestion exposure sender node. Nodes along the path betweenthe PDN-GW and the eNodeB (e.g., as shown the S-GW, the eNodeB, and thefirst router 1004 between the S-GW and the eNodeB) may ECN mark packetsto indicate congestion is experienced (“Mark ECN bit 1013”). The PDN-GWmay provide feedback regarding the ECN markings in the packets toindicate of the level of congestion experienced by the packets(“Feedback ECN Marking 1011”). The eNodeB or base station may receivethe feedback and re-insert feedback or congestion information back intothe network as congestion exposure or re-ECN information (“Re-insertfeedback 1012”). The eNodeB or base station may optionally have apolicer and perform policing. The policing may also or alternatively beperformed at another node (e.g., the first router 1104 or the S-GW. ThePDN-GW may have a dropper and may perform dropping packets based oncongestion information. The dropper may also or alternatively beincluded at another node (e.g., the first router 1104 or the S-GW.

Additional alternate embodiments are contemplated. Having describedembodiment(s) of the invention, alternative embodiment(s) will now bedescribed. Like the previous embodiment(s), these alternativeembodiment(s) are localized congestion avoidance schemes.

A first alternate embodiment pertains to localized explicit congestionnotification (ECN) within a local loop in a cellular network or mobilebackhaul or over a GTP tunnel, whether or not there is also localizedcongestion exposure. For example, an ECN sender may designate an outerheader as ECN capable even when inner headers of packets received by theECN sender are designated not ECN capable. If the inner headers aredesignated ECN capable, the ECN sender may optionally disregard orsubtract the incoming ECN markings. The ECN sender may forward thepackets through a GTP tunnel. One or more other downstream nodes may ECNmark the outer headers even when the inner headers are designated notECN capable. An ECN receiver may return feedback regarding the ECN-CEmarked packets.

A second alternate embodiment pertains to localized ECN or localizedcongestion exposure in a non-cellular or non-mobile backhaul network. Invarious embodiments, a Cable Modem Termination System (CMTS), DigitalSubscriber Line Access Multiplexer (DSLAM), other Digital SubscriberLine (DSL) device, or Multi-service Edge Router (MSER) may incorporatefeatures of an endpoint (sender or receiver) for localized ECN orlocalized congestion exposure as disclosed elsewhere herein.

While the flow diagrams in the figures show a particular order ofoperations performed by certain embodiments of the invention, it shouldbe understood that such order is exemplary (e.g., alternativeembodiments may perform the operations in a different order, combinecertain operations, overlap certain operations, etc.).

In the description and claims, the terms “coupled” and “connected,”along with their derivatives, may be used. It should be understood thatthese terms are not intended as synonyms for each other. “Coupled” isused to indicate that two or more elements, which may or may not be indirect physical or electrical contact with each other, co-operate orinteract with each other. “Connected” is used to indicate theestablishment of communication between two or more elements that arecoupled with each other.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

What is claimed is:
 1. A method of localized congestion exposure withina local loop in a cellular network performed by a localized congestionexposure sender node of the local loop, said method comprising:receiving, at the localized congestion exposure sender node of the localloop in the cellular network, downlink packets destined for a downstreamuser device, and having headers that indicate not explicit congestionnotification capable transport, wherein the localized congestionexposure sender node is a cellular network gateway between a downstreamnode of the local loop and the Internet, and wherein the downstream nodeincludes a wireless base station; receiving packets having feedbackindicating a congestion level experienced by the downlink packets fromthe downstream node of the cellular network, wherein the congestionlevel includes congestion experienced within the downstream node of thecellular network and congestion experienced by the downlink packetsbetween the cellular network gateway and the downstream node; insertinga declaration of an expected downstream congestion level into outerheaders of the received downlink packets, wherein the declaration isbased on the feedback received from the downstream node, and wherein thedeclaration of the expected downstream congestion level includesremaining path congestion information and is to be used to informdownstream nodes of the cellular network of the expected downstreamcongestion level, wherein inserting the declaration of the expecteddownstream congestion level into the outer headers includes insertingthe declaration of the expected downstream congestion level into one ofa General Packet Radio Service (GPRS) Tunneling Protocol (GTP) headersand outer IP headers; detecting based on the feedback whether there isat least one of (a) a malicious flow, (b) a misbehaving user, (c) anaggressive source of traffic, and (d) an overloaded node in the network;and forwarding, through a GTP tunnel, the downlink packets toward thedownstream user device, with the headers that indicate not explicitcongestion notification capable transport as inner headers, and with theouter headers that include the declaration of the expected downstreamcongestion level.
 2. The method of claim 1, wherein the insertingcomprises inserting the declaration of the expected downstreamcongestion level into the outer headers that are indicated as ECNcapable transport, and wherein the inner headers of the downlink packetsindicate not ECN capable transport.
 3. The method of claim 1, whereinthe forwarding comprises forwarding the downlink packets through atunnel, which is not an Internet Protocol (IP) over IP tunnel, whereinthe outer header of the downlink packets forwarded through the tunnelindicate Explicit Congestion Notification (ECN) capable transport. 4.The method of claim 1, further comprising subtracting an incomingExplicit Congestion Notification (ECN) rate from the congestion levelindicated by the feedback.
 5. The method of claim 1, wherein thereceiving the packets having the feedback comprises receiving thepackets having feedback containing information selected from: (1) anumber of packets that were dropped by a base station; (2) a number ofpackets that were dropped by nodes before the base station; (3) a numberof packets that the base station marked to indicate that congestion wasexperienced; and (4) a number of packets marked by nodes before the basestation to indicate that congestion was experienced.
 6. A localizedcongestion exposure sender node configured for localized congestionexposure within a local loop in a cellular network, the localizedcongestion exposure sender node to be deployed in the local loop betweena base station and Internet, the localized congestion exposure sendernode comprising: a first interface configured to receive downlinkpackets destined for a downstream user device, and having headers thatindicate not explicit congestion notification capable transport, whereinthe localized congestion exposure sender node is a cellular networkgateway between a downstream node of the local loop and the Internet,and wherein the downstream node includes a wireless base station; asecond interface configured to receive packets having feedbackindicating a congestion level experienced by the downlink packets fromthe downstream node of the cellular network, wherein the congestionlevel includes congestion experienced within the downstream node of thecellular network and congestion experienced by the downlink packetsbetween the cellular network gateway and the downstream node; and acongestion exposure inserter configured to insert a declaration of anexpected downstream congestion level into outer headers of the receiveddownlink packets, wherein the declaration is based on the feedbackreceived from the downstream node, and wherein the declaration of theexpected downstream congestion level includes remaining path congestioninformation and is to be used to inform downstream nodes of the cellularnetwork of the expected downstream congestion level, wherein to insertthe declaration of the expected downstream congestion level into theouter headers includes to insert the declaration of the expecteddownstream congestion level into one of a General Packet Radio Service(GPRS) Tunneling Protocol (GTP) headers and outer IP headers, andwherein the sender node is configured to: detect based on the feedbackwhether there is at least one of (a) a malicious flow, (b) a misbehavinguser, (c) an aggressive source of traffic, and (d) an overloaded node inthe network, and forward, through a GTP tunnel, the downlink packetstoward the downstream user device, with the headers that indicate notexplicit congestion notification capable transport as inner headers, andwith the outer headers that include the declaration of the expecteddownstream congestion level.
 7. The node of claim 6, wherein thecongestion exposure inserter is configured to insert the declaration ofthe expected downstream congestion level into the outer headers of thedownlink packets that are indicated as Explicit Congestion Notification(ECN) capable transport, and wherein the inner headers of the downlinkpackets indicate not ECN capable transport.
 8. The node of claim 6,wherein the sender node is configured to forward the downlink packetsthrough a tunnel, which is not an Internet Protocol (IP) over IP tunnel,and wherein the outer headers of the downlink packets forwarded throughthe tunnel indicate Explicit Congestion Notification (ECN) capabletransport.
 9. The node of claim 6, further comprising a policerconfigured to subtract an incoming Explicit Congestion Notification(ECN) rate received through the first interface from the congestionlevel indicated by the feedback.
 10. The node of claim 6, furthercomprising a policer configured to detect an aggressive source bydetecting that flows for several users connected to the source all causea high Explicit Congestion Notification (ECN) rate.
 11. The node ofclaim 6, wherein the network node comprises one of a Serving Gateway(S-GW) and a Packet Data Network Gateway (PDN-GW).